Morphological observations on the extracellular space in the macula densa of the mouse kidney.

Basolateral interstitial spaces (BLIS) of the murine macula densa (MD) are dilated in kidneys fixed either by in vivo glutaraldehyde perfusion or snap freezing-freeze substitution, suggesting that macula densa intercellular spaces may be normally dilated in the functioning nephron. BLIS are also dilated in MD with luminal obstruction with "hyaline" cylinder. This finding might indicate a glomerulo-macular fluid and solute streaming, having an impact on the tubuloglomerular feedback mechanism.